At present, there is a considerable amount of software on the market for computer-aided design (CAD) making it possible to store data corresponding to three-dimensional information about objects or a scene to be observed. The software incorporates processing means that enable only a flat image of the object or the scene to be viewed in perspective on a screen at angles of observation that can be selected at will.
Methods of stereoscopic simulation having two view-points have been proposed, e.g. in European patent applications numbers EP-125 480 (HONEYWELL) and EP-172 110 (GIRAVIONS DORAND), however they operate by storing stereoscopic half-images and are therefore not suitable for use with the above-mentioned software.
The Applicant has developed an autostereoscopic video system having more than two elementary images, also referred to as "viewpoints", typically presenting a number n of viewpoints that is equal to 4, and is proprietor of various patents or patent applications relating in particular to an autostereoscopic video picture-taking device, and in particular French patent numbers 87 11764 (FR-2 619 664), 93 05381 (FR-2 705 007), and 93 05383 (FR-2 704 951).
That autostereoscopic video system makes it possible for an observer, without wearing special spectacles, to see images in relief on a screen that is fitted with an optical selector such as a lens array, and to do so under good conditions of visual comfort, given that the observer is not constrained to occupy a precise position for viewing.
The terms "row" and "column" are used respectively to designate horizontal lines and vertical rows of pixels as seen by an observer whether standing or sitting, and independently, for example, of the direction in which a cathode ray display tube is scanned, i.e. horizontally or vertically. For example, on a CRT having vertically oriented scan lines, such scan "lines" will be referred to as "columns".
At present, when displaying stored data as defined above, there is no technical solution making it possible to simulate a display in relief under conditions of visual comfort that enable the autostereoscopic effect to be visible at more than two viewpoints.
Autostereoscopic cameras make use of a lens array, generally an array of cylindrical lenses, and simulation thereof can lead only to a model that is extremely complicated requiring large computer power when generating a complex image having a plurality of interleaved viewpoints that comply with the parameters for autostereoscopy. One such model has been envisaged in the article by Pierre ALLIO entitled "Procede pour la prise de vue video ou la synthese d'images en relief et la visualisation en relief" [A method for taking video pictures or for synthesizing images in relief and for displaying in relief], published in l'Onde Electrique, Vol. 71, No. 1, pp. 26-32, Jan. 1, 1991, Paris. The model envisaged in that article implies implementing a specially modified version of a software package (Turbo CAD 3D) relying on vector forms being generated that are displayed substantially in real time for the purpose of computing images in real time, or for making animated films of synthesized images (but not in real time).
The problem posed by the present invention is thus a problem that is difficult to solve, a priori, and the solutions that can be envisaged would appear, a priori, to exclude applications outside the laboratory.
The invention is based on the idea that, surprisingly, it is possible to simulate an auto-stereoscopic camera, a single camera of the type mentioned above, by means of a plurality of elementary cameras, i.e. by a picture-taking system that is by definition not autostereoscopic and which normally gives rise to large problems of practical implementation, even when there are only two cameras and therefore only two viewpoints, e.g. as in the case of the system known under the name "IMAX 3D" and which turns out to be extremely complex when the number of viewpoints exceeds 2.
Another two-camera apparatus is known from IEEE 1988 International Conference on Consumer Electronics, Rosemont, Jun. 8, 1988, pp. 178-179, Shinichi Yamaguchi "Stereoscopic video movie camera 3D-CAM".
That document relates to a "3D-CAM" camera for taking stereoscopic images from two viewpoints, which images are then displayed in alternation on a screen, viewing being performed through spectacles that are fitted with liquid crystal shutters controlled so as to transmit one image at a time alternately to the left eye and to the right eye.
That document relates to a system for taking images (and not for simulating them) and it has only two viewpoints, a configuration in which problems associated with autostereoscopy do not arise and in which the observer needs to have spectacles or else is constrained to remain in a fixed position relative to the screen.
Yet another two-camera apparatus is known from IEEE Transactions on Consumer Electronics, Vol. 37, No. 1, Feb. 1, 1991, pp. 39-43, Yasuo Takemura "Stereoscopic video movie camera using 300K pixel IT-CCD sensors". While viewing, that apparatus requires the wearing of spectacles fitted with liquid crystal shutters.
European patent application EP-641 132 (MATSUSHITA) relates to a two-camera apparatus for taking pictures in which the angle between the cameras is determined in such a manner as to make binocular fusion of the nearest point possible. That picture-taking apparatus having two viewpoints (i.e. not a simulation) cannot take into account the specific problem associated with autostereoscopy having three or more viewpoints.
According to the invention, simulation is made possible by taking appropriate account of the physical, optical, and perception parameters for an autostereoscopic system having more than two viewpoints.